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Monday, December 7, 2009

Final Causes

This is the conclusion of the comments section in the model comparison chapter (Chapter 20) from Jayne’s book (emphasis original).

It seems that every discussion of scientific inference must deal, sooner or later, with the issue of belief or disbelief in final causes. Expressed views range all the way from Jaques Monod (1970) forbidding us even to mention purpose in the Universe, to the religious fundamentalist who insists that it is evil not to believe in such a purpose. We are astonished by the dogmatic, emotional intensity with which opposite views are proclaimed, by persons who do not have a shred of supporting factual evidence for their positions.

But almost everyone who has discussed this has supposed that by a ’final cause’ one means some supernatural force that suspends natural law and takes over control of events (that is, alters positions and velocities of molecules in a way inconsistent with the equations of motions) in order to ensure that some desired final condition is attained. In our view, almost all past discussions have been flawed by failure to recognize that operation of a final cause does not imply controlling molecular details.

When the author of a textbook says: ’My purpose in writing this book was to…’, he is disclosing that there was a true ’final cause’ governing many activities of writer, pen, secretary, word processor, extending usually over several years. When a chemist imposes conditions on his system which forces it to have a certain volume and temperature, he is just as truly the wielder of a final cause dictating the final thermodynamic state that he wished it to have. A bricklayer and a cook are likewise engaged in the art of invoking final causes for definite purposes. But – and this is the point almost always missed – these final causes are macroscopic; they do not determine any particular ’molecular’ details. In all cases, had those fine details been different in any one of billions of ways, the final cause would have been satisfied just as well.

The final cause may then be said to possess an entropy, indicating the number of microscopic ways in which its purpose can be realized; and the larger that entropy, the greater is the probability that it will be realized. Thus the principle of maximum entropy applies also here.

In other words, while the idea of a microscopic final cause runs counter to all the instincts of a scientists, a macroscopic final cause is a perfectly familiar and real phenomenon, which we all invoke daily. We can hardly deny the existence of purpose in the Universe when virtually everything we do is done with some definite purpose in mind. Indeed, anybody who fails to pursue some definite long-term purpose in the conduct of his life is dismissed as an idler by his colleagues. Obviously, this is just a familiar fact with no religious connotations – and no anti-religious ones. Every scientist believes in macroscopic final causes without thereby believing in supernatural contravention of the laws of physics. The wielder of the final cause is not suspending physical law; he is merely choosing the Hamiltonian with which some system evolves according to physical law. To fail to see this is to generate the most fantastic, mystical nonsense.

So we have the wager from Pascal, and God as the ultimate ’Hamiltonian chooser’ from Jaynes?